1. Field of the Invention
This invention relates to biopharmaceutical material cryogenic preservation methods and apparatus, and more particularly to a biopharmaceutical material cryogenic preservation system and method which maintains a controlled dendritic freezing front velocity.
2. Description of Related Art
Cryopreservation of biopharmaceutical materials is important in the manufacturing, use, storage and sale of such products. For example, biopharmaceutical materials are often cryopreserved by freezing between processing steps and during storage. Similarly, in certain cases, biopharmaceutical materials are frozen and thawed as part of the development process to enhance their quality or to simplify the development process.
When utilizing cryopreservation, the overall quality, and in particular pharmaceutical activity, of the pharmaceutical products is desirably preserved, without substantial degradation of the biopharmaceutical products or solutes.
Currently, in some aspects, cryopreservation of biopharmaceutical materials involves disposing a container comprising the biopharmaceutical materials in a cabinet or chest freezer and allowing the biopharmaceutical materials to freeze. In current cryopreservation techniques, a container enclosing biopharmaceutical materials is placed on a solid or wire-frame shelf in the cabinet or chest freezer. The biopharmaceutical materials are left to freeze until they are solid, in an uncontrolled fashion.
The results from such freezing can be disappointing, to say the least. Significant losses in biopharmaceutical material activity have been noted. For example, observers have noted that stability and conformation of biopharmaceutical materials can be affected by low temperature alone, without any significant changes in variables such as solute concentration or pH.
Further, it has been noted that conventional cryopreservation methods can lead to cryoconcentration, or the redistribution of solutes from the frozen volume to the unfrozen cavity. The result of cryoconcentration can include the crystallization of buffer components leading to a pH change that can affect stability, folding, or even create cleavage of the biopharmaceutical material. Cryoconcentration in conjunction with low temperature effects may cause a decrease in solubility of the biopharmaceutical material, with resulting precipitation.
Finally, damage to the containers has been noted using conventional cryopreservation techniques. Rupture or damage to the integrity of the container is undesirable, as it can compromise sterility or lead to contamination and loss of the biopharmaceutical product.
Accordingly, there is a need for apparatus and methods for cryopreservation of biopharmaceutical materials that solve the deficiencies noted above.
In an aspect, the invention relates to a biopharmaceutical material cryopreservation system comprising a flexible sterile container comprising a biocompatible polymeric material, and the flexible sterile container containing biopharmaceuticals materials, and a freezing system thermally coupled to the biopharmaceutical materials via the flexible sterile container, and the freezing system comprising a temperature sensor that monitors a temperature of the biopharmaceutical materials wherein the freezing system comprises a feedback loop constructed to control a dendritic freezing front velocity, within the biopharmaceutical materials, in a range from approximately 5 millimeters per hour to approximately 250 millimeters per hour based on feedback information from the temperature sensor.
In another aspect, the invention relates to a method for cryopreservation of biopharmaceutical materials, comprising:
providing a flexible sterile container comprising a biocompatible polymeric material, and the flexible sterile container containing biopharmaceuticals materials; thermally coupling a freezing system to the biopharmaceutical materials via the flexible sterile container, and the freezing system comprising (i) a temperature sensor that monitors a temperature of the biopharmaceutical materials, and (ii) a feedback loop constructed to control a dendritic freezing front velocity; and controlling the dendritic freezing front velocity, within the biopharmaceutical materials, in a range from approximately 5 millimeters per hour to approximately 250 millimeters per hour based on feedback information from the temperature sensor.
In yet another aspect, the invention relates to a biopharmaceutical material cryopreservation system, comprising flexible sterile container means for counting biopharmaceutical products, and the flexible sterile container means comprising a biocompatible polymeric material, and the flexible sterile container containing biopharmaceuticals materials, and; freezing means for freezing the biopharmaceutical materials, and the freezing means thermally coupled to the biopharmaceutical materials via the flexible sterile container, and the freezing means comprising a temperature sensor that monitors a temperature of the biopharmaceutical materials wherein the freezing means comprises a feedback loop constructed to control a dendritic freezing front velocity, within the biopharmaceutical materials, in a range from approximately 5 millimeters per hour to approximately 250 millimeters per hour based on feedback information from the temperature sensor.